This is the direct quote from the developer’s post. It clearly states that Gargos is the only one that can kill Tusk, and according to Tusk’s story, he’d need Tusk’s sword to do it.
Additionally, he totally does have regeneration. In the dossiers, after Tusk was attacked by Shadow Jago (who failed to kill him) Hisako took him to a cave so he could do just that.
Dossier VII: Two years ago Tusk was blindsided by one of Gargos’ newest creations - the sinister warrior known as Shadow Jago - who attacked Tusk with an Astral relic: The Oblivion Shard. Unable to kill Tusk, Shadow Jago erased the Immortal’s memories. The swordsman collapsed and fell into a coma, but he was discovered on the snowy plains by the last Astral Gatekeeper who brought him to an ice cave (along with his sword Warg-gram), sealing Tusk inside, and leaving him to regenerate.
The only one who can kill Tusk is Gargos. Otherwise he will just come back, as he’s already demonstrated.
Dude. It’s in the game’s dossier written by the developers. They flat out said it. It’s an established part of the lore. This is already in the game.
How much more proof do you need?
Well shago works as gargos hand doing anything and everything he says and I’m pretty sure gargos wouldn’t mind taking the credit for whatever his minions do.
From what I can tell, the characters that have Ultra Rhythm issues is because they don’t know how to deal with the hitboxes on certain opponents. That’s why Eyedol missed(or misses, I haven’t checked recently) Mira entirely and drops the Ultra.
I do hope that gets fixed ASAP
Oh and another thing. Are we going to know the epilogue of some quests? Because some have cliffhangers. Example, if you play ARIA and get the get the ultratech security level 3 she says something about “so you’re still here. You might prove useful soon.”
It can’t be the fulgore CCIX since we already know she kept that. So what it is? And from the sounds of it she made it long ago.
jk 
